Preference for short term rewards over long term rewards is a hallmark of drug abuse: Drug abusers over-engage now in short term rewards (drug use) that later lead to long term costs, and they under-engage now in constructive activities that would later lead to long term benefits (positive life health functioning). Behavioral economics provides a framework to study such intertemporal choice dynamics. The basic science of behavioral allocation has identified three intertemporal choice processes that influence whether individuals prefer short term or long term rewards (melioration-maximization, temporal discounting, and reward linking). Investigating the role of these choice dynamics in the development of drug abuse and in changes in drug use over time is the goal of this research. The proposed study is a longitudinal, three-group, case control design. College students will be selected based on their marijuana use: abstinent, incipient use, or abuse (n = 70 [35 women and 35 men], N = 210). Key variables to be measured in laboratory sessions at Time 1 and at Time 2 (18 months later) are drug use and related problems, the choice dynamics, substance-related reinforcement in participants' environments, personality variables, and intelligence. The specific aims are to evaluate empirical relations in four areas to determine if the choice dynamics are viable targets for drug abuse prevention: (1) Drug-use group differences on the choice measures would indicate the relevance of the choice processes to drug abuse. (2) Relations between the choice dynamics at Time 1 and changes in drug use from Time 1 to Time 2 would be strong evidence for targeting the processes in prevention efforts. (3) Normal development involves an increasing preference for long-term rewards, but the rate of that progression may be related to stability or change in drug use, which will be investigated in the proposed study. (4) Empirical relations among the three choice dynamics are not known. Evidence for such relations would suggest that the processes could be coherently addressed in prevention interventions. The proposed participants are in a critical developmental transition that involves establishing patterns of behavioral allocation that will significantly impact their functioning in adult roles. This basic research on intertemporal choice dynamics and drug use and abuse during this developmental period may reveal relations that can inform the development of more effective drug abuse prevention efforts. [unreadable] [unreadable]